Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.37	9.461%	$60.6086	$60.61	$60.60	$60.60
Purchase #2	$119.46	10.379%	$131.8588	$131.86	$131.85	$131.90
Purchase #3	$245.62	5.762%	$259.7726	$259.77	$259.75	$259.80
Purchase #4	$55.43	9.819%	$60.8727	$60.87	$60.85	$60.90
Purchase #5	$186.84	4.512%	$195.2702	$195.27	$195.25	$195.30
Purchase #6	$227.76	9.418%	$249.2104	$249.21	$249.20	$249.20
Purchase #7	$115.30	10.316%	$127.1943	$127.19	$127.20	$127.20
7 purchase totals =	$1,005.78		$1,084.7876	$1,084.78	$1,084.70	$1,084.90